The invention relates to enclosed ink cups for pad-type printing machines.
On pad-type printing machines, an image engraved in a metal plate is provided with a thin film of ink by an open air system with a flood bar and a doctor blade or by an enclosed ink cup that is slid over the surface of the plate. The doctor blade or the edge of the cup wipes the engraved surface, leaving the ink at only the engraved image. A silicone pad then transfers the ink image from the plate to the object being printed. A variety of mechanisms have been employed to maintain sealable contact of the doctor blade or ink cup edge on the engraved plate; e.g., springs, magnets, and air cylinders have been used to bias the blade against the plate.
Enclosed ink cups have been proposed in response to environmental and health concerns related to vapors evaporating from exposed ink. For example, Phillip et al. U.S. Pat. No. 4,905,594 describes an enclosed ink cup that has a hollow body that can be bent in the area of its end face and employs a bellows structure to permit relative movement between the area of the end face and the remaining part of the hollow body in order to provide a sealable contact between the ink cup and the printing plate surface on printing plates whose surfaces exhibit deviations from a plane. Phlipp U.S. Pat. No. 4,557,195 describes an enclosed ink cup having a two-piece hollow body. The two parts are movable in relation to each other to ensure exact abutment on the printing plate surface independent of production tolerances. My U.S. Pat. No. 5,320,037, which is hereby incorporated by reference, describes an enclosed ink cup that employs a sheet metal band to make sealable contact with the printing plate.